1. Field of the Invention
The present invention relates to a drive wrench structure, and more particularly to a drive wrench structure that may co-operate with a drive disk to screw a piston into a wheel cylinder or unscrewing the piston from the wheel cylinder, wherein the guide rod of the drive handle may protrude outward from the through hole of the mounting stud when in use, and may be retracted into and fully hidden in the through hole of the mounting stud when not in use, thereby protecting the guide rod of the drive handle, and thereby facilitating storage of the drive wrench structure.
2. Description of the Related Art
In general, the brake system of the automobile includes a brake pedal for operating a brake cylinder which may transmit the hydraulic oil into each wheel cylinder to push the piston in each wheel cylinder, so that the piston may push the brake lining to rub the brake disc, thereby achieving the braking purpose. When the piston is worn out, a drive wrench may be used to assemble and disassemble the piston of the wheel cylinder.
A conventional drive wrench 5 in accordance with the prior art shown in FIG. 5 has an end portion provided with a square drive head 50 that may be inserted into a square mounting hole 60 of a drive disk 6 for rotating the drive disk 6. The drive disk 6 has a periphery provided with an outer flange 61 mounted on the periphery of an end face of the piston 7, the drive disk 6 is provided with an insertion stub 62 that may be inserted into one of multiple insertion recesses 70 formed in the piston 7, for rotating the piston 7, so that the piston 7 may be screwed into the wheel cylinder, and may be unscrewed from the wheel cylinder.
However, the outer flange 61 of the drive disk 6 has a fixed diameter to fit the piston of a fixed size, so that it is necessary to change the drive disk 6 to fit pistons of different sizes, thereby causing inconvenience in use and operation. In addition, the outer flange 61 of the drive disk 6 is mounted on the periphery of the piston 7, so that the driven force arm is longer, thereby wasting the manual work in operation. Further, the outer flange 61 is protruded from the drive disk 6, so that it is easily broken due to hit by a foreign object.
As shown in FIG. 6, the drive disk 6a has a center provided with an inner flange 60a that may be inserted into a depression 71 formed in the center of the outer end face of the piston 7. In operation, when the drive wrench 5 is rotated, the insertion stub 61a may be rotated about the inner flange 60a to push the insertion recess 70 for rotating the piston 7, so that the piston 7 may be screwed into the wheel cylinder, and may be unscrewed from the wheel cylinder. Thus, the driven force arm between the inner flange 60a and the insertion stub 61a may be shortened, thereby saving the manual work. However, the inner flange 60a is protruded from the drive disk 6a, so that it is easily broken due to hit by a foreign object. In addition, the inner flange 60a is easily detach from the depression 71, thereby causing inconvenience in operation.
The present invention has arisen to mitigate and/or obviate the disadvantage of the conventional drive wrench.
The primary objective of the present invention is to provide a drive wrench structure, wherein the guide rod of the drive handle may protrude outward from the through hole of the mounting stud when in use, and may be retracted into and fully hidden in the through hole of the mounting stud when not in use, thereby protecting the guide rod of the drive handle, and thereby facilitating storage of the drive wrench structure.
In accordance with the present invention, there is provided a drive wrench structure, comprising:
a drive handle having one end provided with a threaded rod, the threaded rod having a distal end provided with a guide rod; and
a mounting stud having a first side formed with a screw bore screwed on the threaded rod of the drive handle, and a second side formed with a through hole for passage of the guide rod of the drive handle, with the guide rod of the drive handle protruding outward from the through hole of the mounting stud.